Pressurizable container

ABSTRACT

A container base that is capable of receiving positive internal pressure, such as that created by introducing liquefied gas during a hot filling process, includes either ribs that substantially connect to a standing ring or a draft surface formed on the bottom of the ribs, or a combination of such features.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to plastic containers, and more particularly to plastic containers capable of receiving positive internal pressure.

[0002] Consumers and manufacturers often prefer containers to glass containers for containing comestible products. The safety and appeal of plastic containers for such products have been enhanced by the development of hot-filling processes, in which a product is introduced into the container at an elevated temperature—typically 180 degrees to 190 degrees F.—and sealed.

[0003] Hot filling capabilities have spurred the development of related technologies to address problems of container thermal shrinkage and vacuum-induced deformation. To reduce shrinkage of polyethylene terephthalate (“PET”) containers upon exposure to hot-fill temperatures, for example, PET containers typically undergo a “head-set” process. Often, a PET container is head-set by blow molding at an elevated temperature (compared with those for conventional containers for non-hot-fill applications, such as carbonated soft drinks) for predetermined times, and held at predetermined temperatures for predetermined times. Further, heat set containers are typically formed from a plastic mix having higher intrinsic viscosity that that for bottles suitable only for non-hot-fill, PET applications, such as carbonated soft drinks.

[0004] Head-set PET containers are, thus, able to be filled at conventional hot-fill temperatures with acceptable shrinkage, such as approximately one percent, as for example taught in U.S. Pat. No. 4,863,046 (Collette). Further, heat-treating or heat-setting is taught in a number of patents, including, for example, U.S. Pat. No. 4,233,022 (Brady), U.S. Pat. No. 4,711,624 (Watson), and U.S. Pat. No. 4,219,526 (Mehnert). Each of the patents and applications referred to in the specification is incorporated herein by reference in its entirety.

[0005] Vacuum deformation of a hot-filled container occurs upon capping and cooling after filling with contents at an elevated temperature. Employing vacuum panels or others structure(s) that flex or deform in response to internal container negative pressure has been a popular approach to preventing container collapse upon vacuum deformation. Numerous approaches to vacuum panels in the container sidewalls have been developed. For example, U.S. Pat. Nos. 5,178,289, 5,092,475, and 5,054,632 teach stiffening portions or ribs to increase hoop stiffness and eliminate bulges while integral vacuum panels collapse inwardly.

[0006] Other containers include a pair of vacuum panels, each of which has an indentation or grip portion enabling the container to be gripped between a user's thumb and fingers. For example, U.S. Pat. No. 5,141,120 teaches a bottle having a hinge continuously surrounding a vacuum panel, which includes indentations for gripping. In response to cooling of the container contents, the hinge enables the entire vacuum panel in collapse inwardly. U.S. Pat. No. 5,141,121 similarly teaches a bottle having an outward bulge that inverts in response to cooling of the container contents. Further, bases for heat-set, hot-fillable containers have been developed which are capable of withstanding internal negative pressures common to hot-filling applications. Such bases typically have a continuous standing ring on which the container rests and a ribbed recess portion. For example, U.S. Pat. Nos. 5,503,283; 5,642,826; 4,993,567; 4,993,566; 4,598,831; and 4,108,324 disclose conventional base configurations.

[0007] Often, a continuous standing ring is commercially beneficial because it enables the plastic bottle to mimic the overall appearance of a glass bottle. Further, bases for heat-set, hot-fillable bottles typically have a standing ring that is substantially flat and horizontal in order to accommodate internal negative pressure. In order to promote flexing or deformation of the standing ring, and thereby relieve stress inherent upon vacuum deformation or diminish the magnitude of the corresponding stress risers, such standing rings typically are relatively large.

[0008] Because conventional hot-fillable containers are subjected to negative internal pressure, the ribs of conventional hot-fillable container bases generally are configured to control only inwardly directed forces and deformation. In this regard, the magnitude of inward deformation of a portion of the base typically is inconsequential or unimportant as long as the base is sufficiently strong. The ribs of such bases are generally spaced apart from the standing ring because stiffening proximate the standing ring is unimportant, and because ribs coupled to the standing ring may interfere with the beneficial deformation of the standing ring to compensate for the negative internal pressure. Thus, conventional ribs are typically spaced apart from the standing ring to enable the base to deflect inwardly such that the base may compensate for the negative internal pressure to supplement the vacuum panels. Moreover, if ribs were to contact the standing ring under such conditions, the standing ring would transition quickly from the inner portion that is stiffened by the ribs to the unstiffened portion, which may result in stress risers or otherwise be detrimental to the strength or other attribute of the base.

[0009] U.S. Pat. No. 5,251,424 (ZENGER), which is incorporated herein by reference in its entirety, discloses another approach to enabling a container to accommodate negative internal pressure from a hot-filling application. The '424 patent discloses introducing liquefied gas into the container upon hot-filling to provide a positive internal pressure. Thus, the internal positive pressure counteracts the negative pressure induced by the shrinkage of the contents upon cooling.

[0010] It is a goal of the present invention to provide a base, and corresponding container, that is suitable for a heat-set container that is capable of withstanding positive internal pressure.

SUMMARY

[0011] A base is provided for a heat-set container that is suitable for withstanding internal pressurization without everting. The base includes a standing ring on which the container rests, a recess that extends inwardly and upwardly relative to the standing ring; and plural ribs extending substantially inwardly from the recess. Each one of the plural ribs includes a lower portion that includes a draft surface extending inwardly and upwardly from the standing ring.

[0012] Preferably, the draft surface is directly connected to the standing ring such that the draft surface extends down to a lowermost surface of the container. The angle of the draft surface preferably is approximately five degrees, although the present invention encompasses other ranges, as explained more fully herein. Various geometric relationships are employed to describe the configuration of bases, and it is understood that an independent claim may rely on any single one of the geometric relationships and/or structure described herein, as well as any combination thereof.

[0013] The draft surface deforms substantially downwardly in response to internal pressurization of the container, such as that created upon internal pressurization of the container by introducing liquefied gas upon filling. The container rests on the standing ring even after internal pressurization of the container. The ribs resist eversion of the recessed base surface such that the container is capable of withstanding internal positive pressure. A corresponding method is also provided.

BRIEF DESCRIPTION OF THE FIGURES.

[0014]FIG. 1 is an elevation view of a bottle, with the base shown in phantom, with that illustrates an aspects of the present invention;

[0015]FIG. 2 is a bottom view of the bottle shown in FIG. 1;

[0016]FIG. 3 is an enlarged view of the base shown in FIG. 1;

[0017]FIG. 4 is an enlarged view of the bottom view shown in FIG. 2;

[0018]FIG. 5 is a cross sectional view of the base taken through line 5-5 of FIG. 4;

[0019]FIG. 6 is a cross sectional view of the base taken through line 6-6 of FIG. 4;

[0020]FIG. 7A is a cross sectional view of a portion of the rib taken through line 7A-7A of FIG. 4;

[0021]FIG. 7B is a cross sectional view of a portion of the rib taken through line 7B-7B of FIG. 4;

[0022]FIG. 8A is an enlarged diagrammatic view of a portion of the base shown in FIG. 5;

[0023]FIG. 8B is an enlarged diagrammatic view of the base shown in FIG. 5 with some geometric features labeled;

[0024]FIG. 9A is an enlarged cross-sectional diagrammatic view of a portion of the base shown in FIG. 5; and

[0025]FIG. 9B is an enlarged cross-sectional diagrammatic view of an alternative embodiment to the portion shown in FIG. 9A.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0026] A heat-set container 9 is configured to receive and contain positive internal pressure. Container 9 includes a base 25, a body 12 extending upwardly from base 25, and an upper portion 14 extending upwardly from body 12. Body 12, as shown in FIGS. 1 and 3, preferably is cylindrical. Because container 9 is intended to contain positive internal pressure, complex vacuum panels are not required to collapse or deform in response to negative internal pressure. Even though vacuum panels are not required, the present invention encompasses employing a gripping surface or surfaces, such as finger grips 15, and/or vacuum panels. Thus, the invention contemplates base 25 as described or claimed herein being employed with any container type or configuration.

[0027] Container upper portion 14 includes a dome 16, a neck 18 extending upwardly from dome 16, an opening 20 formed in neck 18, and a finish 22 formed on neck 18 proximate opening 20. Dome 16 yields to body 12 at a lower portion thereof, and smoothly yields to neck 18 at an upper portion thereof. Finish 22 may be any configuration for receiving a closure (not shown) of any type. Preferably, neck 18 is elongated and dome 16 is rounded, although the present invention is not limited to any particular configuration of upper portion 14. A shoulder may be disposed between body 12 and each of base 25 and dome 16, as shown in FIG. 1, or body 12 may smoothly merge into base 25 and dome 16.

[0028] Base 25 includes a heel 30, a standing ring 32, a recess 34, and plural ribs 36. Heel 30 extends downwardly from the lower shoulder and smoothly merges into standing ring 32. Standing ring 32 preferably is substantially continuous. Preferably, standing ring 32 forms a planar surface that is the lowermost point of container 9 either while container 9 is in an unpressurized state or in a pressurized state.

[0029] Recess 34 extends inwardly and upwardly to enclose the underside of container 9. Recess 34 may be substantially frustoconical, have an elliptical, parabolic, or other arcuate shape (in longitudinal cross section, not shown in the figures), or another suitable shape. Plural ribs 36 extend relatively, substantially radially inwardly from recess 34 and stiffen base 25, especially to prevent recess 34 from everting (that is, a structural failure in which at least a portion of recess 34 outwardly collapses or bulges). A recess surface 44, which is disposed between ribs 36, terminates at a top portion or dome 46.

[0030]FIGS. 2 and 4 illustrate base 25 by showing four ribs 36, although the present invention may employ any plural number of ribs. The quantity of ribs will depend upon container base diameter, base thickness, the magnitude of internal pressure, and like parameters, as will be understood by persons familiar with conventional container design and technology in view of the present disclosure. Further, the present invention encompasses employing one or more ribs, as described herein, in combination with conventional ribs (not shown in the Figures). The present invention is described by employing radial ribs, and the present invention encompasses non-radial ribs, such as (but not limited to, those forming a spiral configuration.

[0031] Each one of ribs 36 includes a draft surface 38 and rib face 40, each of which merges with a pair of opposing rib sides 42. Also, a rib upper face 41 may be disposed such that it extends upwardly from rib face 40 so as to merge with recess surface 44 and/or dome 46, as shown in the Figures. Alternatively, rib face 40 may extend upwardly without rib upper face such that rib face 40 thereby forms a substantially continuous angle, radius of curvature, or arc. Employing rib upper face 41, in some configurations, may provide a benefit to plastic flow during the blow molding process as the preform (not shown) expands outwardly and downwardly over an interior of base 25. Further, rib upper face 41 may also provide a larger top portion 46 (compared with the configuration in which rib face 40 extends to and merges directly into top portion 46), which in some configurations may enhance contact with the blow pin (not shown) or with the distal tip of the preform (not shown) during the blow molding process. Portions of surfaces 38, 40, and 41 may be substantially perpendicular to portions of rib sides 42. Rib sides 42 merge with recess surface 44 to fully enclose base 25.

[0032] As best shown in FIGS. 5 through 8, draft surface 38 extends directly from standing ring 32 at its lower end and merges into rib face 40 at its upper end. A draft surface inner point 50 is defined on draft surface 38 proximate rib face 40, and a draft surface outer point 52 is defined on draft surface 38 proximate standing ring 32. Preferably, a line between the draft surface outer point and the draft surface inner point forms a draft angle θ (theta) therebetween relative to a horizontal line, as best shown in FIG. 8A. Draft angle θ (theta) is measured in the container's as-molded state or in the mold, as distinguished from the container's hot or pressurized state, as explained more fully below.

[0033] It is preferred that draft surface 38 be substantially rectilinear—that is, a majority or all of draft surface 38 forms a straight line between draft surface inner point 50 and outer point 52 in longitudinal cross section (that is, in a first plane that is co-planar with a longitudinal centerline CL of container 9 and substantially bisects the subject rib 36) as shown in FIGS. 58A, and 8B. Such a shape generally provides good plastic flow conditions during blow molding and a predictable deformation upon pressurization. Further, draft surface 38 may be either substantially rectilinear or curved in a second cross section that is substantially longitudinal and parallel to the longitudinal centerline CL and perpendicular to the first longitudinal centerline, as shown in FIG. 7. In the embodiment in which draft surface 38 is substantially rectilinear in the second cross section, opposing edges of draft surface 38 may be radiused to smoothly merge into rib sides 42. The present invention is not limited to any particular shape of draft surface, but rather encompasses any shape, including encompassing curves, waves, steps, and the like, as well as encompassing draft surfaces that are not radial.

[0034] The present invention encompasses any draft angle θ (theta), although some angles provide particular advantages. For example, a draft angleθ (theta) approximately equal to zero provides a substantially horizontal surface that may enhance plastic flow during blow molding and that is pushed downwardly relative to standing ring 32 to form small feet. To enable standing ring 32 to remain the lowermost point of the container, draft angle θ (theta) preferably is at least slightly greater than zero. For a preferred embodiment, it has been found that draft angle θ (theta) is at least three degrees, and most preferably five degrees.

[0035] It has also been determined that draft angle θ (theta) preferably is less than 45 degrees to facilitate plastic flow during blow molding. Further, angles of 40 degrees, 30 degrees, and 15 degrees have also been determined to be beneficial in this regard. The width of standing ring 32 preferably is small, which provides the benefits of stiffening the ring and diminishing the transition from stiffened to unstiffened portions. Further, in some circumstances, a wide standing ring may deform outwardly upon internal positive pressurization and destabilize the standing surface. Thus, it has been found that the land dimension or width W (FIGS. 5, 6, 8A, and 8B) of standing ring 32 is less than approximately 0.100 inches. For hot fill beverage bottles of about a 64-ounce size, width W preferably is less than approximately 0.060 inches, and more preferably less than approximately 0.050 inches. In theory, width W could be zero and provide the advantages referred to herein, but a practical lower limit is applied because of blow-molding considerations. As stated herein, the present invention is not limited to such dimensions.

[0036] The magnitude of the variables provided herein may apply to a container of any size, and especially to a container having a base that is consistent with a single serving container, such as about 10 to 16 ounces. Because base 10 may be applied to any size container, some geometric relationships are provided to aid in describing its features. In this regard, referring to FIG. 8B, base 10 may have an overall base diameter A, and a standing ring diameter C, which is defined as the outside rim of standing ring 32. Preferably, standing ring diameter C is between 60% and 80% of base diameter A, and more preferably between 65% and 70% of base diameter A. Thus, it is beneficial, although not strictly necessary, for the heel to have a narrow profile, such as having a heel dimension H no more than approximately 20 percent of base diameter A, and more preferably no more than approximately 10 percent of base diameter A.

[0037] The relationship of diameters A and C is helpful, among other things, to indicate a beneficial geometry of heel 30. Further, standing ring land width W preferably is no more than about four percent of standing ring diameter C, and more preferably no more than about three percent of standing ring diameter C, and even more preferably no more than about two percent of standing ring diameter C.

[0038] A point E is defined at the juncture between draft surface 38 and rib face 40. For the configurations in which draft surface 38 and rib surface 40 are substantially straight (in longitudinal cross section, as shown in FIG. 8B), point E is defined at the intersection between the lines formed by the surfaces. For a configuration in which the juncture between surfaces 38 and 40 is rounded, E may be defined as the midpoint on the surface of the rib between surface 38 and 40. The present invention encompasses configurations in which either or both of draft surface 38 and rib face 40 are curved in transverse cross section. In such a configuration, point E may be defined as the point proximate the junction between surfaces 38 and 40 having the highest rate of change of slope. Draft surface width D is defined as the distance between standing ring 32 and point E. Preferably, draft surface dimension D is no more than approximately one-third A minus four times standing ring land width W (that is, ((A/3)−(4W))). Even more preferably, draft surface dimension D is no more than approximately 80 percent of one-third A minus four times standing ring land width W (that is, 0.80((A/3)−(4W))).

[0039] The depth of rib 36 should be sufficient to resist internal container pressure, as described more fully herein. In this regard, a depth F (measured perpendicular to recess surface 44) of rib 36 near point E preferably is at least D divided by two times cosine theta (that is, (D/(2 cos θ)). Even more preferably, the depth F or rib 36 is at least 1.2 times D divided by two times cosine theta (that is, (1.2 D/(2 cos θ)).

[0040]FIG. 9A diagrammatically shows a cross section of rib 36 taken proximate point E and approximately along line 9A-9A in FIG. 8B. Origin O is defined through the longitudinal centerline CL (FIGS. 1, 5, and 6) of the container 9. Point B₁ is defined as the juncture between rib face 40 and rib side 42,and an angle β₁ is formed between a radial line RL—which intersects point B₁ and origin O—and a centerline line RCL of rib 36. Rib sidewall 42 preferably is substantially collinear with line RL and substantially radial.

[0041] Alternatively, the sidewall of rib 36 may be formed by an angle that is not substantially radial. Such alternative configurations are indicated by sidewalls 42′ and 42″, each of which is shown in dashed lines. First embodiment sidewall 42′ forms an angle φ₁ (measured substantially clockwise—that is, inwardly toward the rib centerline RCL—as oriented in FIG. 9A) from the radial line RL that preferably is no more than approximately angle β₁ plus 5 degrees. Thus, rib 36 may be narrower at its outer potion than at its inner portion. As another alternative, second embodiment rib sidewall 42″ may form an angle φ₂ (measured substantially counterclockwise that is, outwardly away from the rib centerline RCL—as oriented in FIG. 9A) from the radial line RL that preferably is no more than approximately two times angle β₁.

[0042] The present invention is not limited to employing ribs having straight sidewalls. For illustration, FIG. 9B shows a cross section of a rib 36′ that has an arcuate cross section. An angle β₂ is formed between a rib center line RCL and a line between origin O and a point B₂, which is a point on the outer surface of sidewall 36′. Angle β₂ and point B₂ are formed such that angle β₂ is the largest angle at which line RL contacts rib 36′, and point B₂ is the point of contact. Angles φ₁ and φ₂ are formed between line RL and the tangent of the curve formed by the sidewall at point B₂. Thus, the angle formed between the line RL and the tangent taken at point B₂ preferably is within the range of magnitudes of angles φ₁ and φ₂, as described above.

[0043] The present invention is not limited to bases with ribs having the angle ranges disclosed herein, but rather encompasses ribs of any configuration. The geometry of the ribs 36 and 36′ is recited to provide guidance to optimize base performance under some circumstances, but is not intended to limit the scope of the invention unless expressly recited in the claim. Further, the description above employs diameters and a container of circular transverse cross section to describe base 10. The present invention is not limited to containers having such circular cross section, but rather encompasses any cross sectional shape. Thus, for example, diameters A and C may be measured along major or minor axes of an elliptical or oval base, or along the major or minor lengths of a container having substantially flat sides (in transverse cross section).

[0044] Container 9 having base 10 as described herein is intended to be filled at an elevated temperature, and base 10 is configured to receive contents at up to approximately 212 degrees F. without failure, although such temperature is not a limit to the scope of the invention. In this regard, a plastic resin having an intrinsic viscosity of over 0.75 may be employed, and most preferably an intrinsic viscosity of approximately 0.84 may be employed. The present invention is not limited to such viscosities, which are provided only for guidance.

[0045] Upon introduction of the contents into container 9, a predetermined quantity of liquefied gas is introduced therein. The liquefied gas, which preferably is liquefied nitrogen, quickly vaporizes. After capping, such vaporization increases the internal pressure within container 9. Preferably, the internal pressure range is 15 to 35 psi at hot-fill temperature, and 0 to 10 psi upon cooling to ambient temperature (that is, approximately 72 degrees). The pressure ranges are provided to be exemplary, and the scope of the present invention is not limited to such pressure ranges.

[0046] Co-pending U.S. patent application Ser. No. ______ (Attorney Docket Number CC-3412), entitled “Method For Diminishing Delamination Of A Multilayer Plastic Container,” and co-pending U.S. patent application Ser. No. ______ (Attorney Docket Number CC-3449), entitled “Method For Extending The Effective Life Of An Oxygen Scavenger In A Container Wall,” describe nitrogen dosing techniques with which the container according to any aspect of the present invention may be employed. Further, U.S. Pat. Nos. 5,955,527; 5,639,815; 5,049,624; and/or 5,021,515 disclose an oxygen scavenging material that is suitable for use in bottles in hot-fillable and other containers, and that may be employed in container 9. Each of the applications and patents referred to herein is incorporated herein by reference in its entirety.

[0047] Techniques for introducing liquefied gas into container 9 are well known, especially by persons familiar with such technology for introducing liquefied nitrogen into metal cans. Such nitrogen dosing systems are commercially available and nearly exhaustively described in the literature. The present invention is not limited to a particular means for introducing liquefied gas, but rather encompasses any introduction technology. The magnitude of the dose of liquefied gas introduced into the container may be determined according to such parameters as contents temperature, headspace volume, characteristics of the container (including its elasticity or relationship between volume change and pressure), order of introduction of the product and nitrogen dose (that is, whether the nitrogen dose is introducing into the container before, concurrently with, or after the contents), and the time period between introducing the nitrogen dose and capping or sealing. Choosing the magnitude of the dose of liquefied gas for a particular application will be straightforward for persons familiar with liquefied gas dosing technology, such as, for example, as used in the metal can industry, in light of the present disclosure and the above parameters.

[0048] The internal positive pressure within container 9 acts on all surfaces of base 10. Thus, pressure urges top portion or dome 46 substantially downwardly, urges against the interior surfaces of recess 34 and ribs 36 substantially downwardly and substantially inwardly, urges against the interior surface of standing ring 32 substantially downwardly, and urges against the interior of heel 30 substantially outwardly and somewhat downwardly. Each of the downward components of the pressure vectors, as well as most of the other components of the pressure vectors, urges base 10 toward eversion. The term “substantially downwardly” as used herein refers generally to the downward direction when the container is upright, and nay also include a lateral component.

[0049] Conventional bases often fail under such conditions either by complete eversion, which is a complete failure mode in which much of recess 34 is pushed fully out the bottom of base 10 to break the plane defined by standing ring 32, or by partial eversion, in which a portion of standing ring 32 (most often at a single circumferential location) is pushed downwardly relative to the plane defined by the as-molded standing ring. Even a partial eversion of small magnitude might destroy or inhibit the container's ability of the container to solidly rest on a flat surface or its ability to stand.

[0050] Standing ring 32 is stiffened by ribs 36, thereby diminishing downward deflection of standing ring 32, upon pressurization of base 10, compared with an unstiffened configuration. Draft surface 38 being directly connected to standing ring 32 enhances such stiffening. Also, because standing ringland dimension or width W, as described above, is small (compared, for example, to configurations common to hot-fill bottles that are subject to internal negative pressure), the total force and moments acting on standing ring 32 (about, for example, the interface between heel 30 and standing ring 32) contributes to keeping the deformation of standing ring 32 small.

[0051] Thus, the stiffening of standing ring 32 by ribs 36 and the standing ring's small dimension W each enhance the stability of container 9 when standing upright on standing ring 32 and inhibiting partial or localized eversion. Each of such features may be employed independently of the other such that the present invention is not limited to employing both features. Rather, the present invention encompasses a base employing a standing ring having the dimensions provided herein in combination with ribs that are spaced apart therefrom. As well, the present invention encompasses a base employing ribs that extend from the standing ring in combination with a standing ring having a dimension W that is outside that described herein.

[0052] Upon pressurization of container 9, draft surface 38 deforms downwardly such that, for the embodiment in which draft surface 38 is flat in its as molded state, draft surface 38 forms a convex bow (relative to a plane) in draft surface 38 when viewed from below base 10. Further, the draft angle θ (theta) decreases upon such pressurization. The magnitude of the bow may be small, such as a few thousandths of an inch for containers in the 48 to 64 ounce container size. Alternatively, if draft surface 38 is sufficiently stiff, by, for example, the stiffening effect of rib sides 42 on draft surface 38, draft surface may deflect downwardly by a few thousands in such a way that no bow if formed. Thus, the present invention encompasses any deflection or deformation of draft surface 38.

[0053] Preferably, draft surface 38 in its fully deformed or deflected state (that is, upon pressurization of container 9 as described herein), does not interfere with standing ring 32 such that standing ring 32 remains circumferentially continuous. in this regard, draft surface 38 does not extend downwardly below standing ring 32 even in its deformed or deflected state such that substantially all of standing ring 32 is substantially planar. However, the present invention encompasses any configuration in which draft surface 38 deflects downwardly in response to internal pressurization, as described above.

[0054] Persons familiar with preform and blow molding processes and technology in light of the present disclosure will be enabled to configure a container that employs the present invention(s), such as a container base in which its draft surface deforms as described above.

[0055] Further, a method is provided in which hot-fillable container base 10 is provided that is capable of receiving positive internal pressure. Upon introducing hot product contents and introducing liquefied gas and subsequent sealing or capping, draft surface 38 flexes downwardly about its junction with standing ring 28 or about a draft surface outer point 52 proximate standing ring 28, and may otherwise perform as described above with respect to the description of the structural aspects of base 10.

[0056] The geometry of draft surface 38 and the width of standing ring 28 each contribute to the capability of base 10 to receive internal positive pressure as described above. The present invention, however, is not limited to simultaneously employing both (or any other) features described herein, but rather each feature may be employed alone or with any other feature to provide the positive pressure capabilities. 

We claim:
 1. A heat-set, pressurizable container suitable for filling at an elevated temperature, said container comprising: a body; an upper portion extending upwardly from the body and including a finish and an opening therein; an enclosed base disposed below the body, said base including: a standing ring on which the container rests; a recess that extends inwardly and upwardly relative to the standing ring; and plural ribs extending substantially inwardly from the recess, each one of the plural ribs including a lower portion that includes a draft surface extending inwardly and upwardly from the standing ring; whereby (i) the draft surface deforms substantially downwardly in response to internal pressurization of the container, (ii) the container rests on the standing ring even after internal pressurization of the container, and (iii) the ribs resist eversion of the recessed base surface such that the container is capable of withstanding internal positive pressure.
 2. The container of claim 1 wherein the container is formed of a heat-set plastic.
 3. The container of claim 1 wherein the internal pressurization is formed by introducing a liquefied gas into the container prior to capping.
 4. The container of claim 1 wherein the draft surface is substantially linear, in a first longitudinal cross section that is coplanar with a longitudinal centerline of the rib, while the container is in an unpressurized state.
 5. The container of claim 4 wherein the draft surface is substantially planar while the container is in an unpressurized state.
 6. The container of claim 4 wherein the draft surface is curved in a second longitudinal cross section that is perpendicular to the first longitudinal cross section.
 7. The container of claim 1 wherein the draft surface is directly connected to the standing ring.
 8. The container of claim 1 wherein each one of the plural ribs include a face surface that extends inwardly from the draft surface.
 9. The container of claim 8 wherein draft surface includes a outer point proximate the standing ring and an inner point proximate the rib face, a line between the draft surface outer point and the draft surface inner point forming a draft angle relative to a horizontal line that is between approximately 0 degrees and 45 degrees.
 10. The container of claim 9 wherein the draft angle is between about 3 degrees and about 40 degrees.
 11. The container of claim 9 wherein the draft angle is between about 5 degrees and about 30 degrees.
 12. The container of claim 9 wherein the draft angle is between about 5 degrees and about 15 degrees.
 13. The container of claim 9 wherein the draft angle is between about 5 and 25 degrees.
 14. The container of claim 9 wherein the draft angle is about 5 degrees.
 15. The container of claim 9 wherein the draft surface is directly coupled to the standing ring proximate the draft surface outer point and is directly coupled to the rib face proximate the draft surface inner point, whereby the draft surface couples the standing ring and the rib face together.
 16. The container of claim 9 wherein the standing ring defines a standing ring diameter and a standing ring land width, and the draft surface has a radial dimension of no more than approximately one-third the standing ring diameter minus four times the standing ring land width.
 17. The container of claim 16 wherein the draft surface radial dimension is no more than approximately 80 percent of one-third the standing ring diameter minus four times the standing ring land width.
 18. The container of claim 16 wherein the ribs have a depth measured proximate the draft surface that is at least the draft surface radial dimension divided by two times cosine of the draft angle.
 19. The container of claim 16 wherein the ribs have a depth measured proximate the draft surface that is at least 1.2 times the draft surface radial dimension divided by two times cosine of the draft angle.
 20. The container of claim 1 wherein the standing ring is substantially continuous and circumferential.
 21. The container of claim 1 wherein the standing ring is circumferentially discontinuous.
 22. The container of claim 21 wherein the standing ring is interrupted by the draft surface of the ribs.
 23. The container of claim 1 wherein the standing ring has a width that is less than approximately 0.100 inches.
 24. The container of claim 23 wherein the standing ring width is less than about 0.060 inches.
 25. The container of claim 23 wherein the standing ring width is less than about 0.050 inches.
 26. The container of claim 23 wherein the standing ring width is less than about 0.025 inches.
 27. The container of claim 23 wherein the standing ring width is about 0.10 inches.
 28. The container of claim 18 wherein the standing ring width no more than approximately four percent of standing ring diameter.
 29. The container of claim 18 wherein the standing ring width no more than approximately three percent of standing ring diameter.
 30. The container of claim 18 wherein the standing ring width no more than approximately two percent of standing ring diameter.
 31. The container of claim 23 wherein the standing ring width is as small as the blow molding process will allow.
 32. The container of claim 1 wherein the base further includes a heel extending upwardly from the standing ring toward the body.
 33. The container of claim 32 wherein the heel is coupled to the base.
 34. The container of claim 1 wherein the upper portion includes a dome from which the finish extends.
 35. The container of claim 34 wherein the upper portion includes an elongated neck extending from the dome, the finish formed on the neck.
 36. The container of claim 1 wherein the base further includes a heel that is coupled between the standing ring and the body, the standing ring defines a standing ring diameter, and the heel has a radial heel dimension that is no more than approximately 20 percent of the standing ring diameter.
 37. The container of claim 36 wherein the heel radial dimension is at least approximately 10 percent of the standing ring diameter.
 38. The container of claim 36 wherein the heel radial dimension is more than approximately 17.5 percent of the standing ring diameter.
 39. The container of claim 38 wherein the heel radial dimension is at least approximately 15 percent of the standing ring diameter.
 40. The container of claim 1 wherein the standing ring defines a standing ring diameter that is between approximately 60% and approximately 80% of a base diameter.
 41. The container of claim 40 wherein the standing ring diameter between approximately 65% and approximately 70% of the base diameter.
 42. The container of claim 1 wherein the internal pressurization is between approximately 15 and approximately 35 psi at hot fill temperatures.
 43. The container of claim 1 wherein the internal pressurization is between approximately 0 and approximately 10 psi at ambient temperatures.
 44. The container of claim 1 wherein said container is formed of a material having an intrinsic viscosity greater than approximately 0.75.
 45. A heat-set, pressurizable container suitable for filling at an elevated temperature, said container comprising: a body; an upper portion extending upwardly from the body and including a finish and an opening therein; an enclosed base disposed below the body, said base including: a standing ring on which the container rests; a recess that extends inwardly and upwardly relative to the standing ring; and plural ribs extending substantially inwardly from the recess, each one of the plural ribs including a lower portion that includes a draft surface extending inwardly and upwardly from the standing ring, the draft surface being directly coupled to the standing ring and forming a draft angle of between approximately 0 degrees and approximately 45 degrees, the draft surface is directly coupled to the standing ring proximate a draft surface outer point and is directly coupled to the rib face proximate a draft surface inner point, whereby the draft surface couples the standing ring and the rib face together.
 46. The container of claim 44 wherein the draft angle is between about 3 degrees and about 40 degrees.
 47. The container of claim 44 wherein the draft angle is between about 5 degrees and about 30 degrees.
 48. The container of claim 44 wherein the draft angle is between about 5 degrees and about 15 degrees.
 49. The container of claim 44 wherein the draft angle is about 5 degrees.
 50. The container of claim 44 wherein the standing ring has a width that is less than approximately 0.100 inches.
 51. The container of claim 44 wherein the standing ring width is less than about 0.075 inches.
 52. The container of claim 44 wherein the standing ring width is less than about 0.050 inches.
 53. The container of claim 44 wherein the standing ring width is less than about 0.025 inches.
 54. The container of claim 44 wherein the standing ring width is less than about 0.10 inches.
 55. A method of filling a container with a flowable product, said method comprising: providing a container comprising a body and a base, the base including: a standing ring on which the container rests; a recess that extends inwardly and upwardly relative to the standing ring; and plural ribs extending substantially inwardly from the recess, each one of the plural ribs including a lower portion that includes a draft surface extending inwardly and upwardly from the standing ring; introducing hot contents and liquefied gas into the container; sealing the container before all of the liquefied gas vaporizes to create a positive internal pressure within the container; whereby the draft surface deforms substantially downwardly in response to internal pressurization of the container, the container rests on the standing ring even after internal pressurization of the container, and the ribs resist eversion of the recessed base surface such that the container is capable of withstanding internal positive pressure. 